PT spectroscopy of the Rabi problem

TL;DR

This paper explores how non-hermitian, PT-symmetric periodic perturbations affect a two-level quantum system, revealing complex phase transitions including symmetry breaking and restoration at various frequencies.

Contribution

It introduces a detailed phase diagram for PT-symmetric Rabi systems, highlighting novel phenomena like multiple symmetry-breaking and restoring frequency windows.

Findings

Small perturbations cause symmetry breaking near resonances.

High-frequency perturbations can restore PT symmetry.

Multiple frequency windows exhibit alternating symmetry phases.

Abstract

We investigate the effects of a time-periodic, non-hermitian, PT-symmetric perturbation on a system with two (or few) levels, and obtain its phase diagram as a function of the perturbation strength and frequency. We demonstrate that when the perturbation frequency is close to one of the system resonances, even a vanishingly small perturbation leads to PT symmetry breaking. We also find a restored PT-symmetric phase at high frequencies, and at moderate perturbation strengths, we find multiple frequency windows where PT-symmetry is broken and restored. Our results imply that the PT-symmetric Rabi problem shows surprisingly rich phenomena absent in its hermitian or static counterparts.